Involuntary attention and brightness contrast.
Carrasco, Ling, and Read (2004) reported that involuntary attention increased perceived contrast. We replicated Carrasco et al. and then tested an alternative hypothesis: With stimuli near threshold, a peripheral cue biased observers to believe a stimulus had been presented in the cued location. Consistent with this hypothesis, the effect disappeared when we used higher-contrast stimuli. We further tested the guessing-bias hypothesis in three ways: (1) In a detection experiment, the cue affected bias, but did not increase d'; (2) when the cue followed the stimulus, we obtained the same results as when the cue preceded the stimulus; (3) in one experiment, some trials contained no stimulus, yet observers responded that the cued blank stimulus had higher contrast than the uncued blank stimulus. The results suggest that the effects of a noninformative peripheral cue are best described in terms of nonperceptual biases.
Prinzmetal
William
W
Psychology Department, University of California, Berkeley, CA 94720, USA. wprinz@berkeley.edu
Long
Virginia
V
Leonhardt
James
J
D001288:Attention; D015350:Contrast Sensitivity; D003463:Cues; D006801:Humans; D008027:Light; D014836:Volition